package com.twq.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//     如何让浏览器刷新
        resp.setHeader("refresh","3");
//        在内存中创建图片
        BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);
        Graphics2D g =  (Graphics2D)bufferedImage.getGraphics();
//设置图片颜色
        g.setColor(Color.BLUE);
        g.fillRect(0,0,80,20);
        g.setColor(Color.gray);
        g.setFont(new Font(null,Font.BOLD,20));
        g.drawString(makeNum(),0,20);
        //用图片方式打开

        resp.setContentType("image/jpeg");
//        不让浏览器缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");

//        把图片写给浏览器
       ImageIO.write(bufferedImage,"jpg",resp.getOutputStream());


    }

    private String makeNum(){
        Random random = new Random();
        String num = random.nextInt(9999999) +"";
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i <7-num.length() ; i++) {
            stringBuffer.append("0");

        }
       String s= stringBuffer.toString()+num;
        return num;
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    }
}
